Ball mill discharge trommel



P 27, 1965 D. J. VELCHEFF 3,180,581

BALL MILL DISCHARGE TROMMEL Filed July 19, 1962 4 Sheets-Sheet 1 w M fINVENTOR. DONHAD J VELCf/EFF April 27, 1965 1:..1. VELCHEFF ,1 5

BALL MILL DISCHARGE TROMMEL Filed July 19, 1962 4 Sheets-Sheet 2INVENTOR. 004 520 J VLC//FF A TTORNEYS'.

April 27, 1965 1:..1. VELCHEFF 3,180,581

BALL MILL DISCHARGE TROMMEL Filed July 19, 1962 4 Sheets-Sheet 3"""l'lll.

INVENTOR A T TOPA/[Yi 5 zi wzgww Ap 27, 1965 D. J. VELCHEFF 3,180,581

BALL MILL DISCHARGE TROMMEL Filed July 19. 1962 4 Sheets-Sheet 4INVENTOR Dom/740 J V54 CHEFF A 7'TORNEVS Zildfifidi Patented Apr. 27,1965 3,180,581 BALL MILL DISCHARGE TROMMEL Donald J. Velchefl, SilverBay, Minn, assignor to Reserve Mining Company, Silver Bay, Minn, acorporation of Minnesota Filed July 19, 1962, Ser. No. 210,975 3 Claims.(Cl. 241-79) The invention relates to grinding mills, such as ball millsor the like, and more particularly relates to novel and improved meansfor automatically intercepting and removing the oversize product at thedischarge end of such mill. Merely as an example, the invention will bedescribed in its application to the grinding of ore in any one ofseveral steps, in each step of which there is utilized a ball millequipped with my improved oversize discharge interceptor.

In a ball mill, for example, the previously crushed ore, within apreferred size range, is tumbled with hardened steel balls, the orebeing introduced at a charging end and being caused to progress towardsa discharge end. At said discharge end the damp material is movedthrough a rotating, cylindrical trommel screen through which screen theproperly sized ground product falls on a conveyor or through a conduit,ready for the next comminution step.

' The still-oversize lumps which are too large to fall through thetrommel screen openings, are moved to an end opening, where, in thenormal practice in the art, they fall into a box or bin. This receptaclemust be kept from overflowing, and it has been customary for the ballmill operator to periodically shovel the oversize lumps into a cartwhich is later emptied into a return conveyor to the same or a similarmill for recirculation through the grinding circuit.

A mill operator usually controls the slurry density in known manner, butit requires fairly constant observation, and attention, to controlcertain effective factors, and any time spent in clearing the oversizepermits a possible unobserved or uncontrolled variation in one or otherof the aforesaid factors, so that it is most desirable to devise meansfor automatically clearing the oversize from the discharge trommelwithout requiring any attention from the mill operator. In this way asingle operator has more time for his function ofcontrolling theuniformity of the slurry density and he can more efl'iciently maintain acheck on a plurality of mills.

An object of the present invention, therefore, is to automatically clearthe oversized lumps of ore at the grinding mill discharge end, anddirect them into receptacles of larger than usual capacity, whichreceptacles are adapted to be readily removed while being replaced bysimilar units.

Other objects and advantages will be apparent from a study of thefollowing specification, in conjunction with the accompanying drawings,in which:

FIG. 1 is a vertical sectional view taken axially through the dischargeend of a ball mill.

FIG. 2 is a vertical sectional view taken on the line 2--2 of FIG. 1.

FIG. 3 is a sectional view of a portion of FIG. 1, but somewhatenlarged.

FIG. 4 is a sectional view taken on the line 44 FIG. 1.

FIG. 5 is an elevational view of my improved pickup trommel ring withpart of the front flange broken away to reveal internal structure.

FIG. 6 is a fragmentary side edge view of the trommel ring as it wouldbe seen fromthe position of the line 6-6 of FIG. 5.

The embodiment of the invention shown in the drawings comprises pick-upand discharge means afiixed on the left end of a ball mill 20, thedischarge end of which is shown in FIGS. 1 and 3. The ball mill is theusual generally cylindrical drum having an end wall 21 provided with anaxially extending hub 22 rotatable in bearings 23 on a base 24. Similarbearing and support means are provided for the charging end (not shown)of the mill. The mill has a large ring gear 25 which is in mesh with adriving pinion 26 for rotating the mill assembly. The gears, pinions,motors, gear reduction devices, etc., used for driving purposes areconventional and need not be here shown.

The tumbling slurry, at a level at least as high as the dotted line 27in FIG. 1 iiows into and through the discharge neck 28 which is providedwith an internal helical flange 29.

The slurry flows through neck 28 and into a cylindrical trommel screen30 which likewise is provided with a helical internal flange 31.

The trommel screen Si is supported within a cage consisting of end rings34 and 35 which are connected by struts 36. The trommel screen 30, theend rings 34 and 35, the neck 23 and the hub 22 are all attached to thegrinding mill, and rotate therewith. It will be noted that therespective helices 29 and 31 are oppositely inclined, for the followingreason. The rotation of the mill is in such direction that the helix 29opposes any tendency of the upper level balls in the mill to escapethrough neck 28, without opposing gravity iiow of slurry. The helix 31assists gravity flow of the slurry through the trommel, permitting theundersize to fall through.

Supported on the discharge end of the cage is an elevating ring orannulus 37 which is attached to end ring 34 by bolts 38. It has tworadially extending parallel wall flanges 39 and 40 connected by an outerperipheral wall 41, to thereby afford a radially inwardly openingchannel 44. This channel is interrupted at spaced points by partitions45, best seen in FIG. 5, connected to the opposite walls 39 and All. Itcan be noted that any oversize lumps carried through the trommel 36)will drop into the annulus 37 as indicated by the arrow 46 (lower leftof FIG. 3) and since the annulus is rotating with the mill, thepartitions will carry the lumps upwardly (FIG. 4) until they havereached the critical height to cause them to drop by gravity out of theannulus, hereinafter termed an elevator ring. As they drop they areintercepted by a spout shaped chute 47 which is pivotally carried on'apintle or rod 48 which is rotatable in end brackets 45?. The bracketsare mounted on a cover 50 swingable on hinges 51 carried on the machineframe 52 (FIG. 2) and the chute has a discharge tip end 47a extendingoutwardly through an opening 53 (FIG. 2) in the cover. The chute directsthe oversize lumps into a cart 54 (FIGS. 1 and 2) which is movable oncasters 55 but which may also be removed by means of an overhead crane(not shown) which picks up the cart by means of a bail 56.

In order to permit the mill to continue to run for a brief period whilea full cart is being replaced by an empty one, the chute 47 can beflipped to the dotted line position in FIG. 3, whereupon the overisizelumps will be directed inwardly into the trommel. This expedient need beresorted to only for a brief period, and it prevents the oversizematerial from being discharged onto the floor.

The elevator ring 37 is provided with slots 57 in its peripheral wall toallow seepage of excess water into the mill discharge outlet which isshown at 53 in FIG. 1 and which need not be more fully described. Thenormall mill output which falls through the trommel screen 30 alsopasses out through the discharge outlet 5?.

The peripheral wall of the elevator ring is shown as being provided withslots 59 (FIG. 6) although this is optional.

From a consideration of the structure described herein it is apparentthat interception and removal of over-sized fragments of the work loadproceed automatically until the cart 54 is filled, at which time anothercart may be substituted immediately. The elevator ring and chuteinterceptor eliminatelaborious clearing of the hitherto customary catchboxes and leaves the operator free to observe and control the milloperation, with particular attention to the slurry density leaving bythe mill outlet,

The ring or annulus 37 may be considered as of U= shaped or channeledsectional contour, having a circumferential outerwall 41 and two opposedparallel side walls 39 and 40. The partitions 45 which form weirs orpartitions across the inwardly opening channel carry the mate: rialupwardly as the annulus rotates, as hereinabove previously described.

7 What is claimed is:

1. Rotatable grinding mill discharge means including a cylindricaltrommel having a discharge end opening towards which a slurried groundagglomerate is advanced as the mill and trommel rotate, said trommelhaving screen wall means through which under-sized material falls andupon which oversized material is advanced to said dis charge end, achanneled annulus fixed at said discharge end opening, and rotating withsaid trommel and having a circumferential outer wall, and two opposedparallel side walls extending radially inwardly part way to the axis ofrotation to leave a central opening in registry with the trommeldischarge opening, a plurality of partitions spaced around the channel,each partition being disposed transversely across the channel whereby,when the annulus rotates, oversized material moving from the trommelinto the annulus is carried around and upwardly by said partitions aseach partition successively moves upwardly and then inclines inwardlybeyond the horizontal, and a chute in fixed position within the trommelcentral opening, and

in the general vertical plane of the trommel, so as to.

intercept such dropping material and guide it outwardly and downwardlybeyond said plane of the annulus, said 2. Rotatable grinding milldischarge means including a cylindrical trommel having a discharge endopening towards which aslurried ground agglomerate is advanced as themill and tromrnel rotate, said mill having a discharge neck axially'alignedrwith and connected to said trommel, said trommel havinginternal helical flanges extending inwardly from its inner wallesurface.and tending to direct material towards itsfdischarge end, said dischargeneck also having internalihelical flanges running in a direction counterto that of the flanges in the trommel, said flanges in. the dischargeneck extending inwardly from its inner wall surface and tendingtorestrain escape of grinding elements from the grinding mill, achanneled annulus fixed at said discharge end opening, and rotatingwithsaid trommel and having a circumferential outer fall, and twoopposed parallel side walls ex.- tending radially inwardly part way tothe axis of rotation to leave a central opening in registry with thetrommel discharge opening, a plurality of partitions spaced around thechannel, each partition beingdisposed transversely across thechannel-whereby,-when the annulus rotates,

"oversized material moving from the trommel into the annulus is carriedaround and upwardly by said partitions as each partition successivelymovesupwardly and then inclines inwardly beyond the horizontal, and achute in fixed position within the trommel central opening, and in thegeneral vertical plane of the trommel, so as to intercept such droppingmaterial and guide it outwardly and downwardly beyond said plane of theannulus.

3. Apparatus as defined in claim 2 wherein said chute is pivotallymounted to permit reversal of its position whereby to return oversizedmaterial into the trommel as desired.

References Cited by the Examiner UNITED STATES PATENTS 740,879 10/03Lindhard 241-171 XR 794,843 7/05 Beneke .'241-17l XR 1,368,739 2/21Lindhard 24 170 XR 2,099,133 11/37 Munro et al 24l70 XR 2,730,307 1/56Demarest 241-171 XR J. SPENCER OVERHOLSER, Primary Examiner.

1. ROTATABLE GRINDING MILL DISCHARGE MEANS INCLUDING A CYLINDRICALTROMMEL HAVING A DISCHARGE END OPENING TOWARDS WHICH IS SLURRIED GROUNDAGGLOMERATE IS ADVANCED AS THE MILL AND TROMMEL ROTATE, SAID TROMMELHAVING SCREEN WALL MEANS THROUGH WHICH UNDER-SIZED MATERIAL FALLS ANDUPON WHICH OVERSIZED MATERIAL IS ADVANCED TO SAID DISCHARGE END, ACHANNELED ANNULUS FIXED AT SAID DISCHARGE END OPENING, AND ROTATING WITHSAID TROMMEL AND HAVING A CIRCCUMFERENTIAL OUTER WALL, AND TWO OPPOSEDPARALLEL SIDE WALLS EXTENDING RADIALLY INWARDLY PART WAY TO THE AXIS OFROTATION TO LEAVE A CENTRAL OPENING IN REGISTRY WITH THE TROMMELDISCHARGE OPENING, A PLURALITY OF PARTITIONS SPACED AROUND THE CHANNEL,EACH PARTITION BEING DISPOSED TRANSVERSELY ACROSS THE CHANNEL WHEREBY,WHEN THE ANNULUS ROTATES, OVERSIZED MATERIAL MOVING FROM THE TROMMELINTO THE ANNULUS IS CARRIED AROUND AND UPWARDLY BY SAID PARTITIONS ASEACH PARTITION SUCCESSIVELY MOVES UPWARDLY AND THEN INCLINES INWARDLYBEYOND THE HORIZONTAL, AND A CHUTE IN FIXED POSITION WITHIN THE TROMMELCENTRAL OPENING, AND IN THE GENERAL VERTICAL PLANE OF THE TROMMEL, SO ASTO INTERCEPT SUCH DROPPING MATERIAL AND GUIDE IT OUTWARDLY ANDDOWNWARDLY BEYOND SAID PLANE OF THE ANNULUS, SAID CHUTE BEING PIVOTALLYMOUNTED TO PERMIT REVERSAL OF ITS POSITION WHEREBY TO RETURN OVERSIZEDMATERIAL INTO THE TROMMEL.